pH regulation in adult rat carotid body glomus cells. Importance of extracellular pH, sodium, and potassium.
pH regulation in adult rat carotid body glomus cells. Importance of extracellular pH, sodium, and potassium.
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DOI：
10.1085/jgp.100.4.593
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发表时间：
1992-10
影响因子：
3.8
通讯作者：
Roos, A
中科院分区：
文献类型：
--
作者：
Wilding, T J;Cheng, B;Roos, A
在新鲜分离的成年大鼠颈动脉体的灌注（36℃）单个血管球（I型）细胞中跟踪细胞内pH（pHi）的过程。细胞已加载 pH 敏感荧光染料 2',7'-(2-羧乙基)-5（和-6）-羧基荧光素。采用高K(+)-尼日利亚菌素法进行校准。在 pHo 7.40 且无 CO2 的情况下，血管球细胞的 pHi 为 7.23 +/- 0.02 (n = 70)；在 5% CO2/25 mM HCO3- 中，pHi 为 7.18 +/- 0.08 (n = 9)。 pHi 对 pHo 的变化非常敏感。没有 CO2 时，δ pHi/δ pHo 为 0.85（pHo 6.20-8.00；32 个细胞），而在 CO2/HCO3 中，无论 pHo（6.80-7.40；14 个细胞）在恒定 PCO2 或恒定 [HCO3-]o 下变化，该比率均为 0.82。血管球细胞对 pHo 的高度 pHi 敏感性只有人类红细胞能与之媲美。球细胞中存在活性 Na+/H+ 交换器（表观 Km = 58 +/- 6 mM）：去除 Na+ 或添加阿米洛利衍生物 5-(N,N-六亚甲基)-阿米洛利可导致 pHi 下降 0.9。这些细胞的膜还含有 K+/H+ 交换器。将 [K+]o 从 4.7 升高至 25、50 或 140 mM 可逆地分别使 pHi 升高 0.2、0.3 和 0.6。 Rb+ 没有影响，但在相应浓度的 Tl+ 中碱化比 K+ 中的碱化快得多。将 [K+]o 降低至 1.5 mM 可使 pHi 降低 0.1。这些 pHi 变化被证明不是由于膜电压的变化引起的，并且在不存在 Na+ 的情况下更加引人注目。随着 pHi 降低，固有缓冲能力（在名义上不存在 CO2 的情况下，产生小幅 pHi 上升所需的强碱量）从 3 mM 增加至约 21 mM，但在 pHi 6.60 以下时几乎保持不变。拟合表达式假定存在一种“等效”细胞内缓冲液（pK 6.41，41 mM）。 pHi 对 pHo 的异常敏感性表明球细胞的 pHi 是化学感受器对外部酸度反应的一个环节。
The course of intracellular pH (pHi) was followed in superfused (36 degrees C) single glomus (type I) cells of the freshly dissociated adult rat carotid body. The cells had been loaded with the pH-sensitive fluorescent dye 2',7'-(2-carboxyethyl)-5 (and -6)-carboxyfluorescein. The high K(+)-nigericin method was used for calibration. The pHi of the glomus cell at pHo 7.40, without CO2, was 7.23 +/- 0.02 (n = 70); in 5% CO2/25 mM HCO3-, pHi was 7.18 +/- 0.08 (n = 9). The pHi was very sensitive to changes in pHo. Without CO2, delta pHi/delta pHo was 0.85 (pHo 6.20-8.00; 32 cells), while in CO2/HCO3- this ratio was 0.82 irrespective of whether pHo (6.80-7.40; 14 cells) was changed at constant PCO2 or at constant [HCO3-]o. The great pHi sensitivity of the glomus cell to pHo is matched only by that of the human red cell. An active Na+/H+ exchanger (apparent Km = 58 +/- 6 mM) is present in glomus cells: Na+ removal or addition of the amiloride derivative 5- (N,N-hexamethylene)-amiloride induced pHi to fall by as much as 0.9. The membrane of these cells also contains a K+/H+ exchanger. Raising [K+]o from 4.7 to 25, 50, or 140 mM reversibly raised pHi by 0.2, 0.3, and 0.6, respectively. Rb+ had no effect, but in corresponding concentrations of Tl+ alkalinization was much faster than in K+. Reducing [K+]o to 1.5 mM lowered pHi by 0.1. These pHi changes were shown not to be due to changes in membrane voltage, and were even more striking in the absence of Na+. Intrinsic buffering power (amount of strong base required to produce, in the nominal absence of CO2, a small pHi rise) increased from 3 to approximately 21 mM as pHi was lowered, but remained nearly unchanged below pHi 6.60. The fitted expression assumed the presence of one "equivalent" intracellular buffer (pK 6.41, 41 mM). The exceptional pHi sensitivity to pHo suggests that the pHi of the glomus cell is a link in the chemoreceptor's response to external acidity.